In one of the prior art devices, the electro optic switch operates in the 1/2 .lambda. mode with a Glan-Taylor polarizer on the left and rochon polarizer on the right. The 100 percent reflecting mirror is a porro prism which is retroreflective about one axis. The Glan-Taylor polarizer reflects the horizontal polarization to one side of the polarizer and passes the vertical polarization. The Glan-Taylor polarizer is calcite to achieve separation of the two polarizations. The rochon polarizer separates the two polarizations angularly passing the vertical polarization undeviated and deviating the horizontal polarization to one side. The retroreflective property of the porro prism requires that the two polarizations from the rochon polarizer be separated a minimum of one-half beam diameter at the porro prism. Calcite is also required for the rochon polarizer to achieve the necessary angular separation.
Procurement of polarizers for some prior art electro optic switches including the aforementioned device are a considerable problem because they are not readily available and are often poor in quality.
The principal advantage of the wedge polarizer configuration is that it does not require calcite, as in some of the prior art devices, for the polarizing material, since a large angular separation of the two polarizations is not required. The reason for this is that both wedges deviate the two polarizations angularly about the same axis. This permits the electro optic switch to be oriented with a porro prism such that in the off condition, both polarizations are misaligned angularly with the porro prism.
The quartz wedges are considerably less expensive and are more easily mounted and aligned in the laser. Quartz is also a more durable material than calcite and is not as easily damaged by the laser beam.